Dados do Trabalho

Title

Additional contribution of the stable environment in time-lapse incubator for women over 38 years of age

Objective

Since the advent of the time-lapse incubator, it has been widely used around the world with the aim of selecting the best quality embryo based on morphokinetic characteristics. However, the time-lapse system allows continuous observation of the embryos without removing them from the incubator, which can bring other benefits due to the more stable culture environment than conventional incubators. The aim of this study was to evaluate blastocyst development and ongoing pregnancy rates according to the type of incubator used for embryo culture in women over 38 years old (≥38yo), compared with younger women (<38yo), undergoing ICSI cycles.

Methods

This was a retrospective cohort study including 177 ICSI cycles performed between December 2020 and March 2021 in a private IVF clinic in São Paulo. In those period, conventional and time-lapse incubators were being used concomitantly in the embryology laboratory. Embryos were cultured in one of the incubator randomly. The embryos selection for transfer was based on morphological characteristics, independently of incubator. We have excluded fertility preservation cycles, oocyte donation cycles or frozen-thawed oocyte cycles, and 137 ICSI cycles were included in this analysis, as 80 cycles in the time-lapse incubator (TL group) and 57 in the conventional incubator (CONTROL group). Cycles were also split according to women age, as <38yo or ≥38yo.

Results

For women ≥38yo, the outcomes of cycles included in the TL (n=37) and CONTROL (n=32) groups were compared. The demographic characteristics were similar (age: 40.5±2.0 and 40.5±1.6; p=0.664 / presence of male factor: 8% and 6%; p=0.740 / MII collected: 5.5±4.4 and 5.9±4.4; p=0.610, respectively). Despite of cycles had equivalent basement characteristics, the blastocyst development rate was higher in embryos cultured in time-lapse than conventional incubator (53.9% versus 34.1% p=0.019). Moreover, cumulative pregnancy rate was expressively higher in TL group compared to conventional (33.0% and 19.0%; p=0.214), despite of no statistically significant, in women ≥38yo. For younger women (<38yo), the cycles included in the TL (n=43) and CONTROL (n=25) groups were compared (age: 35.8±4.6 and 36.4±5.1; p=0.735 / presence of male factor: 14% and 16%; p=0.818 / MII collected: 13.1±11.7 and 7.1±4.2; p=0.014, respectively). The blastocyst development rates were similar (56.7% and 59.3%; p=0.673) and cumulative ongoing pregnancy rates did not differ between groups (50.0% and 48.0%; p=0.865). The multiple logistic regression model confirmed the higher blastocyst development rate is associated to increased chances of pregnancy (OR 0.03; p= 0.038) in women ≥38yo; but it do not in younger women (OR: 0.01; p=0.529) adjusted for confounders (MII oocytes collected and PGT-A).

Conclusion

When embryo selection is based in the morphological characteristics, the embryo culture in a time-lapse incubator does not seem to affect the laboratorial or clinical outcomes for young women (<38yo). On the other hand, for women ≥38yo, the time-lapse incubator contributes to promoting a higher rate of blastocyst, which in turn is associated with greater chances of pregnancy. Therefore, the more stable environment of time-lapse incubator during culture time seems to support blastocyst formation when the oocytes are impaired by the advanced women’s age

Keywords

time-lapse incubator, conventional incubator, ICSI, embryo development, advanced maternal age